Hi Tim,<div><br></div><div>When dealing with lidar data, I always import using r.in.xyz first. You can easily vary the resolution to generate a quick preview and it will give you a sense of the data source and what information it contains. If you then find you need to do more advanced processing, you can move over to the lidar tools. </div>
<div><br></div><div>Cheers,</div><div><br></div><div>Jamie<br><br><div class="gmail_quote">On Thu, Mar 10, 2011 at 10:23 AM, TimNorwey <span dir="ltr"><<a href="mailto:timmy_weyrer@live.at">timmy_weyrer@live.at</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Hi all!<br>
<br>
Iīm trying to generate a DEM/DSM out of LIDAR data that I have downloaded<br>
from the website <a href="http://atlas.lsu.edu/lidar/" target="_blank">http://atlas.lsu.edu/lidar/</a> .<br>
<br>
The data can be downloaded as .csv-file. Within this file no attribute names<br>
are given. For test purpose I manipulated the .csv, so that "only" 10,000<br>
points were left and I added a row at the top "x,y,z" as attribute names.<br>
<br>
After doing that I imported the .csv into QGIS using the Plugin "Add<br>
Delimited Text Layer", stored the points as .shp-file and imported them into<br>
GRASS GIS database using v.in.ogr (as 3D points).<br>
<br>
Then I tried to follow the workflow described on the website<br>
<a href="http://grass.osgeo.org/wiki/LIDAR#LIDAR_Tools" target="_blank">http://grass.osgeo.org/wiki/LIDAR#LIDAR_Tools</a> (I started at "DEM/DSM<br>
separation the more complex way").<br>
<br>
The first step should be the use of v.extract to separate first and last<br>
pulse laser points. Because of the reason that I have no information about<br>
first/last pulse laser points, I skipped this step and tried to follow the<br>
other steps. But I think this was for nothing, because v.lidar.edgedetection<br>
needs the last pulse laser points and v.lidar.growing needs the first pulse<br>
laser points. So I donīt write more about this...<br>
<br>
I really donīt know how to generate a DEM/DSM based on this data and it<br>
would be nice if anyone of you has an idea. Is there a possibility to do<br>
generate a DEM/DSM without using the steps that are described within the<br>
WIKI page above?<br>
<br>
What do you think about the import of the .csv into GRASS GIS via QGIS? Is<br>
there an easier way to import it?<br>
<br>
If you need any further information to understand my problem, just let me<br>
know.<br>
<br>
Tim<br>
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